1. Field of the Invention
The present patent application for industrial invention relates to a coffee machine of the type used in bars, which is adapted to provide for measured cup filling.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
The peculiarities and advantages of the invention will become evident after a short description of the prior art with relevant drawbacks.
First of all, a general description of the structure and operation of a coffee machine is given below.
Such a machine is provided with an inlet for water from the water system and with a series of pipes used to take the water through suitable heating elements, and pour pressurized water inside the filter-holders that are suitably pre-loaded with pressed coffee powder and provided in lower position with one or two coffee dispenser nozzles.
The passage of the hot water through the layer of coffee powder produces the desired beverage, basically in emulsion state, and its fall by gravity inside the cups disposed under said dispenser nozzles.
Starting from such a technology, it must be considered that the taste of espresso bar drinkers can be very different: some customers do not indicate any particular preference, but many of them make a precise request, asking for a “short” (strong) or “long” (weak) coffee.
In most cases, in order to satisfy the different requests from customers, the operator visually checks the level reached by the coffee in each cup in real time and stops distribution when he believes that the coffee has reached a medium level (for a “normal” espresso), a minimum level (for a “short” espresso) or a maximum level (for a “long” espresso).
More precisely, in order to stop the distribution of coffee, the operator actuates the stop command of the pump used to provide the hot water flow towards the filter-holder.
Evidently, such an operation is very approximate and surely not capable of ensuring the uniform filling of the cups used to make and serve a “short” or a “long” coffee.
In order to make the task of the operator easier and less empirical, professional coffee machines are equipped with an automatic device that is able to guarantee the constant filling level of the cups by suitably cooperating with the electronic control unit provided in the coffee machine.
Practically speaking, the device is a volumetric flow meter mounted along the water conduit that takes the hot water towards the dispenser unit of the coffee machine.
Moreover, according to the customer's request, the electronic control unit is programmed with the information about the amount of water that is necessary to obtain a “normal”, a “short” or a “long” coffee.
Because of the cooperation with said flow meter, the electronic control unit is informed in real time about the actual amount of hot water that is flowing towards the dispenser unit of the coffee machine.
In view of the above, the electronic unit can interrupt the hot water flow as soon as it is informed about the passage of the correct amount of water (which has been previously set in the electronic unit) for the specific customer's request for a “normal”, a “short” or a “long” coffee.
Because of this operating principle, a coffee machine should guarantee the standardized constant filling level for every “short”, “normal” or “long” coffee distributed during its operation.
In practice, nevertheless, such an operating principle has proved to be unsatisfactory.
In fact, although it is true that the volumetric flow meter exactly evaluates the amount of hot water that reaches each filter-holder, it is also true that it cannot control the variables that affect the way in which each hot water dose actually interferes with the coffee powder contained in the filter-holder.
Being installed upstream the filter-holder, the volumetric measuring device cannot consider two parameters that variably affect the amount of coffee actually distributed for each cup.
First of all, reference is made to the water dispersion that occurs in the section of the water circuit comprised between the measuring device and the filter-holder, and secondly to the compression level and/or granulometry of the coffee powder inside the filter-holder (which certainly affect the amount of water that can reach the dispenser nozzles of the filter-holder, after passing through the layer of pressed coffee powder).
In view of the above, it is impossible to say with certainty that all “short” coffees will reach the same level in the cups, in spite of starting from the same amount of hot water detected by the volumetric flow meter.
The evaluation of such a drawback has led to the additional evolution of the prior art—disclosed in patent WO2012146641—that has finally assured that each coffee cup used to produce a “short” coffee is exactly filed with the same amount of coffee loaded in all other cups used to produce a “short” coffee, either before or after.
In particular, the invention claimed in the aforementioned prior document provides for a typical professional coffee machine equipped with a weighing device, actually a load cell, applied to the horizontal tray used to support the cups to be filled under the filter-holders.
By means of a suitable electronic control unit, cooperation is obtained between said load cell and the devices used to send hot water towards each filter-holder and enable the distribution of coffee.
Such cooperation guarantees that the electronic control unit is able to precisely indicate the time when the distribution of coffee must be interrupted.
In particular, such an indication is given as soon as, in view of the cooperation with said load cell, the control unit is informed that each cup has reached the same weight, net of tare, as a predefined amount of coffee (i.e. beverage) that corresponds to a “normal”, a “short” or a “long” coffee, respectively.
In any case, the fact that said load cell detects the amount of coffee downstream the filter-holders avoids the risk that the value detected from time to time (in terms of distributed coffee) is negatively affected—as in the prior art—by dispersions along the water conduit of the coffee machine or by the higher or lower absorption of water by the coffee powder pressed inside the filter-holders.
However, it must be noted that even the latest technology has shown a functional limitation that prevents the use of such a technology in the professional coffee machines used in bars.
Such a functional limitation derives from the position of said load cell directly under the grille where the cups are positioned to receive the coffee that drips from the filter-holders.
However, because of its position under the filter-holders, such a grille usually receives by gravity the residues of the coffee powder loaded in the filter-holders, as well as the coffee drippings that come out from the filter-holders also after removing and serving the cups.
Considering that the grille is characterized by the presence of numerous slots, it is easy to understand that the solid and liquid residues poured on the grille inevitably get said load cell dirty and clogged, thus altering its correct operation mode.